Pittsburgh, PA -- A fire ignited in a three-unit apartment when plumbers were trying to thaw frozen pipes, firefighters believe.

Fire crews were called to a major fire yesterday. Sharpsburg Police Chief Leo Rudski said, "We were told there were plumbers in the home around 2:30, thawing out a line, but we don't know what type of equipment they were using."

A first floor tenant told fire crews that plumbers were upstairs when the fire ignited. "There [were] plumbers upstairs and I think they got part of the wall on fire and then they bailed, I don't know," said Dave Widcorreck.

Another tenant who lived on an upper floor left her apartment before the fire, but said that plumbers came to her door earlier that day, but she told them her pipes were fine.